This paper discusses new pulse compression codes in which the modulation phase is monotonoically increased or decreased and the phase difference between the neighboring modulated codes is compressed to polyphase. In the proposed coding system, the sidelobe is small when the compression ratio is relatively low. Even in the high Doppler frequency region in which the pulse shape of the 13-bit Barker codes is largely deformed, the shape of the compressed pulse is stable and the sidelobe is always smaller than in the 13-bit Barker code. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 81(10): 41–49, 1998